After helping keep sand on the Waikiki shoreline throughout 93 years of seasonal waves, currents and tides, storms and rising seas, the Royal Hawaiian Groin, a rock-and-concrete jetty that extends out into the blue-green waters of Waikiki before gently curving toward Diamond Head, is now in the midst of its own sea change.

Work to reconstruct the old jetty began in early May and should be completed before the end of July, said Sam Lemmo, administrator of the state Department of Lands and Natural Resources Office of Conservation and Coastal Lands, which is overseeing the project and splitting the $1.5 million construction cost with the Waikiki Beach Special Improvement District Association, which is funded by a special tax based on the property values of the businesses within the district.

The reason for the old groin’s face-lift was the fear that, should it collapse, the sandy beach on its Diamond Head side would be swept away by erosion. “Structural engineers found the aging groin to be at risk for falling,” the website of the nonprofit Waikiki Improvement Association says.

After a plan to replace it with a T-shaped groin met with opposition from surfers, including members of Save Our Surf and Surfrider Foundation, who said during a DLNR public hearing in 2017 that it would ruin Waikiki’s waves, the design was ultimately modified into an L-shape that echoed the contours of the original.

Construction by Kiewit Infrastructure West Co., with Sea Engineering as project consultant, was scheduled for the fall, but DLNR and WBSIDA agreed to start the job when, in late March, Waikiki became deserted following Gov. David Ige’s 14-day quarantine order and Mayor Kirk Caldwell’s beach-sitting ban.

“We knew the beaches would be cleared and decided to push the pedal on construction because it would would be very difficult to accomplish with the beach full of tourists,” Lemmo said.

The new, approximately 160- foot-long groin, which is being built around the old one, will have two layers of rock on both sides and a new concrete top with a ridge down the middle, raising the elevation by 1-1/2 feet, he said.

“It doesn’t follow the exact footprint of the old Royal Hawaiian groin, which is basically a wall that goes out 270 feet,” Lemmo said. “Our new groin does a turn at 90 feet, the point where the old groin (slopes) underwater.”

If the T-head groin had been built, it would have “benefited a small beach to form on its Ewa side,” in the Grays Beach area fronting the Halekulani Resort, said Dolan Eversole, a coastal processes specialist with the University of Hawaii Sea Grant College Program and Waikiki Beach management coordinator for the district association.

If the new groin is successful, it might help muster public support for a future series of T-head groins along Waikiki Beach, Eversole and Lemmo said.

Eversole added that in addition to stabilizing the beach, the new groin will play a part in mitigating the effects of sea level rise.

Erosion is a continual process, said Rick Egged, president of WIA, noting that Waikiki Beach was replenished with 24,000 cubic yards of sand in 2012, “and we’ve lost 25-30% of it.” The public-private partnership, he added, aims to add another 24,000 cubic yards early next year.